Conventionally, when a semiconductor device, such as an IC or an LSI (Large Scale Integrated Circuit), which has PGA (Pin Grid Array)-type terminals is connected to a circuit board such as a printed wiring board, the terminals are electrically connected to conductive traces on the circuit board via a ZIF (Zero Insertion Force) socket mounted to the circuit board (see, for example, Japanese Patent Application Laid-Open (kokai) No. 2002-352928).
FIG. 8 is a partial sectional view showing a conventional socket. Reference numeral 301 denotes a housing of a socket used for connecting a packaged semiconductor device 310 to a circuit board; more specifically, for electrically connecting pin terminals 311 of the semiconductor device 310 to unillustrated electrodes of the circuit board.
The housing 301 is formed of an insulating material such as resin, and has accommodation holes 302 which are arranged to correspond to the pin terminals 311 and extend through the housing 301 in the thickness direction thereof. Connection terminals 303 to be connected to the pin terminals 311 are disposed in the accommodation holes 302. Solder balls 304 to be connected to the electrodes of the circuit board are bonded to the lower ends of the connection terminals 303. A plate-shaped slide member 305 is disposed on the housing 301 to be slidable in a lateral direction. The slide member 305 is formed of an insulating material such as resin, and has connection holes 307 which are arranged to correspond to the pin terminals 311 and extend through the slide member 305 in the thickness direction thereof.
A rotation support metal member 312 having a cam support hole of radius R1 formed therein is attached to an end of the housing 301. A pressure-receiving metal member 306 having a cam support hole of radius R2 formed therein is attached to an end of the slide member 305. The center axis of the cam support hole of the pressure-receiving metal member 306 deviates in the lateral direction from the center axis of the cam support hole of the rotation support metal member 312 by an amount δ. An eccentric cam 315 is disposed to pass through the cam support hole of the rotation support metal member 312 and the cam support hole of the pressure receiving metal member 306.
When the semiconductor device 310 is to be attached to the socket, first the slide member 305 is set to a ZIF position as shown in FIG. 8. Subsequently, the semiconductor device 310 is placed on the slide member 305, while the pin terminals 311 are inserted into the corresponding connection holes 307. Thus, distal end portions of the pin terminals 311 enter the accommodation holes 302 of the housing 301. At this time, since the slide member 305 is set to the ZIF position, the distal end portions of the pin terminals 311 can enter the accommodation holes 302 with small likelihood of coming into contact with the connection terminals 303 and receiving insertion resistance therefrom.
Subsequently, when an operator turns the eccentric cam 315 through operation of an unillustrated lever, by the action of the eccentric cam 315, the slide member 305 is moved rightward in FIG. 8. As a result, the semiconductor device 310 is also moved rightward in FIG. 8, and the distal end portions of the pin terminals 311 are moved rightward and are connected to the connection terminals 303. In this manner, the pin terminals 311 of the semiconductor device 310 can be electrically connected to the electrodes of the circuit board.
However, in the conventional socket, the pin terminals 311 may be bent at the time of attachment of the semiconductor device 310, for the following reasons. Since the slide member 305 is interposed between the semiconductor device 310 and the housing 301, the length of the pin terminals 311 increases by an amount corresponding to the thickness of the slide member 305, and the position accuracy of the distal end portions of the pin terminals 311 decreases, whereby the distal end portions of the pin terminals 311 become more likely to improperly come into contact with the connection terminals 303 and receive lateral forces therefrom. In addition, because of the increased length, the pin terminals 311 become likely to bend.
Since the slide member 305 is slid by use of the eccentric cam 315, the structure becomes complex, and cost increases. In addition, use of the eccentric cam 315 makes it difficult to cope with increasing density of the pin terminals 311. When the semiconductor device 310 is attached to the socket, all the pin terminals 311 must be inserted into the corresponding connection holes 307. Therefore, positioning of the semiconductor device 310 is difficult, and the easiness of operation of attaching the semiconductor device 310 is spoiled. Moreover, when the semiconductor device 310 is attached to the socket, a check must be made as to whether the slide member 305 is located in the ZIF position. Since such checking is performed on the basis of the position of the lever, the checking operation is difficult to perform. Therefore, the semiconductor device 310 may be placed on the slide member 305, which has not yet been set to the ZIF position, and the pin terminals 311 may improperly come into contact with the connection terminals 303 and bend.